Account Value – The Account Value provides the total of all cash + current positions – margin requirements. Basically, this is the full value of the account if you liquidated everything.
Margin Balance – This balance money is held for insurance against positions, either stock or options, and also money held for potential borrowing (ie. 50% of stock position). This can represent the amount of money you are borrowing to buy stock on margin. But it can also include risk capital that is being held in your account but restricted from use to cover options risk.
For individual short options this is 25% of the stock price – the out of the money amount between the strike price and the current stock price.
For credit spreads it will represent the amount between the short and long option.
Buying Power Section – This area will show much money is available for use by the positions below.
Stock – How much money is available for use to buy stocks including funds available to borrow on margin.
Option – Usually is cash available for spending value.
Day Trading – Usually is four times the cash available. Note: There are additional requirements for day trading. This should be reviewed on your brokerage site.